Gold holds a special place in the imagination of cultures across the world, and is one of the earth's most precious metals. We know that 5000 years ago, ancient Egyptians were making beautiful jewellery from gold, and the tradition continues today.
But did you know that most gold jewellery contains other metals too? Pure gold is generally considered too soft to be hardwearing enough for everyday wear, and also carries a very high price tag, so most of the gold used in jewellery is 'alloyed' or mixed with other metals, and this is indicated by the 'carat' of a piece of gold.
A carat is one twenty-fourth of the total amount of metal contained in the piece of gold jewellery. So, for instance, a woman's wedding ring may be eighteen carat gold. This means that three quarters of the gold (eighteen twenty-fourths) is pure gold. The other quarter will usually be made up of copper, or zinc. Twenty-four carat gold is pure gold, with no other metal present.
Take a look at the hallmark on a modern piece of gold jewellery however, and you won't see the number of carats. What you'll see instead is a much higher number, indicating the parts of gold per thousand parts of metal. So an eighteen carat gold piece of gold jewellery will be marked with the figure 750 shown in an octagonal outline. This is known as the millesimal mark and indicates that the jewellery contains 750 parts (three quarters) gold, to 250 parts (one quarter) other metals.
So, using the same principle, if the piece of jewellery is hallmarked with a millesimal mark of 375, it's nine carat, with 585 it's fourteen carat, and with 916, it's twenty-two carat.
The choice of the other metals in gold is crucial, as depending on the alloy metals, the colour of the gold jewellery can change. If you mix gold with just copper, you produce 'rose' gold, which has a distinctive pink tinge. Nine carat rose gold will be pinker than eighteen carat rose gold as, of course, the content of the copper is higher.
White gold is an increasingly popular choice for gold jewellery and is produced by mixing pure gold with palladium or silver, to produce a silvery grey coloured gold, which is often brightened by giving it a rhodium plating.
Two other stamps will also appear as part of the hallmark on a piece of modern gold jewellery. The first of these is the identifying stamp of the Assay Office which tested the gold content of the item. If it's been 'assayed' or tested in the UK, it will have been done in one of just four offices: Edinburgh, London, Birmingham or Sheffield, although every Assay Office across the world has its own stamp which can be traced.
The other stamp which will always appear is the 'sponsor's mark'. This will indicated which company has sent the item for hallmarking. Originally, this would have always been the maker of the item. These days, it could also be the retailer or importer of the piece of gold jewellery.
But there may be other stamps on your gold jewellery too. A letter stamp will indicate the year of testing, and if you're interested, it's fairly easy to look up which year it was tested online. Commemorative stamps are very popular in the UK, and have been used in the years of the Queen's Coronation and both her jubilees (all show the Queen's head in profile), as well as for the new Millennium in 2000 (indicated by the figure 2000 in a cross).
The Hallmarking (Exempted Articles) Orders 1982 and 1986 specify a weight threshold of 1 gram for the hallmarking of gold jewellery. Where the weight of gold in a piece is less than 1 gram, a hallmark does not have to be shown. Interestingly, in relation to earrings, or pendants and chains, each individual element is separately governed by the weight threshold for hallmarking purposes, rather than the combined weight of gold used.
So next time you put on a piece of your gold jewellery, whether it's gold earrings, a pendant, a watch or a gold ring, take a quick look to see if it bears a hallmark and use your new-found knowledge to learn a little bit more about it’s history!